This may sound strange, but a lot of covid weakness is caused by a low amount of oxygen getting through the arteries / blood vessels that are shrunk tight because of low amount of nitric oxide. You should have foods with nitrates that the body uses to make nitric oxide to allow the arteries to open up.
They say the best way to increase nitric oxide is to have dark greens. The darker the better. When we chew the greens, the good bacteria in our mouth creates the nitric oxide. (Remember, no mouthwash or toothpaste with fluoride that could knock out the good bacteria.)
I try for a type of curly Italian kale, like dinosaur or Lucinato / Tuscan that looks tough but is tender. ( Other choices are arugula or spinach. ) I rinse the kale well and than pull it off the stems and cut it up with kitchen shears.
Beets are a great source of nitrate and you could put some on the greens.
Blueberries are good and could also be added to the salad or have by themselves.
Watermelon is a good source.
If you could find unsweetened cocoa and add honey. I put it in decaf coffee, but you could add or use milk or almond milk instead.
Nuts and celery are a good source, so a nut butter on celery sticks would be good.
Also include some orange slices for vitamin C which is an antioxidant that helps with nitric oxide production.